diff --git a/obmc/mapper/server.py b/obmc/mapper/server.py
index 32d8080..de5d65d 100644
--- a/obmc/mapper/server.py
+++ b/obmc/mapper/server.py
@@ -274,7 +274,7 @@
                 '{} discovery failure on {}\n'.format(
                     self.bus_map.get(owner, owner),
                     path))
-            traceback.print_exception(*sys.exc_info())
+            traceback.print_exception(*sys.exc_info(), file=sys.stderr)
             del self.defer_signals[owner]
             del self.bus_map[owner]